The type of torsion damping device described above is for example used in clutches of the kind commonly referred to as "lock up" clutches, forming part of the hydrokinetic coupling apparatus, of the kind with which automobiles having automatic or semi-automatic transmission may be provided.
An example of such an arrangement is the lock up clutch which is the subject of the French Patent Application No. 2 518 202.
The resilient members which are provided are distributed in two groups, with the phasing ring, which is also freely rotatable, transmitting the forces exerted by each of the resilient members on a first one of these groups to the corresponding resilient member of the other group, thus providing the series mounting which is required.
In operation, the phasing ring is, in addition, subjected to the centrifugal forces to which the resilient members are also subjected.
If the resilient members are regularly spaced apart circumferentially, if they are all subjected to exactly the same centrifugal force, and if they all develop exactly the same thrust force, the resultant of the corresponding radial forces is then zero. The phasing ring, which would be in perfect equilibrium, would not be urged into a radial displacement at all.
In practice, the above is rarely true, so that, since the resultant of the radial forces is in fact not zero, the phasing ring is subjected to a certain amount of radial displacement.
In order that such displacement does not interfere with the operation of assembly, it is necessary to associate with the phasing ring some kind of retaining means which are adapted to maintain the phasing ring radially, in some convenient manner, with respect to the axis of the assembly.
One of the coaxial parts concerned includes a rotatable plate, which hereinafter will be referred to as a hub plate, while the other coaxial part includes two rings which will hereinafter be referred to as guide rings. The guide rings are arranged on either side of the hub plate, and are spaced at a distance from the latter. The guide rings are secured at intervals to each other by fastenings. In order to achieve this, it has been proposed, in French Patent Application No. 2 518 202 and mentioned above, that this radial restraint of the phasing ring should be obtained by means of the guide rings, with the latter constituting, in any suitable way, a casing which is circumferentially continuous around the phasing ring.
It follows from this that it is necessary to give to at least one of the guide rings a particular configuration, with an axial wall of which is circumferentially continuous. This increases the cost of the assembly.
In addition, the guide rings are also adapted to provide abutment means for the resilient members, and it is therefore necessary that the rings shall be of metal. Since the same is true for the phasing ring, contact between the phasing ring and the guide rings is necessarily in the form of metal to metal contact.
Now, it is preferable to avoid such metal to metal contact, since this can give rise to tearing of the metal and lead to malfunctioning.